Holographic television record system

ABSTRACT

A method and apparatus for constructing and replaying an optical holographic record containing a plurality of very small holograms, each of which contains information, independent of the other holograms. In the preferred embodiment described, each frame of an ordinary photographic movie is recorded as an individual hologram. The record is a narrow and elongated film with the holograms formed in a line along its length, each hologram touching those on either side thereof. A moving image is reconstructed by drawing the record at a uniform speed through an effectively continuous wave coherent light beam. A light sensitive detector for converting an image into a time varying electronic signal is positioned to receive reconstructed sequence of images and transform it into a signal acceptable to an ordinary television set for displaying the movie thereon. Each hologram is constructed by passing a beam of a coherent light through a movie frame onto a much smaller hologram aperture and by interfering this beam at a finite angle with a reference wavefront having a radius of curvature substantially equal to the effective distance between the movie and the hologram. Methods of adding color visual information as well as sound information are also disclosed. Such a holographic record is copied onto a photopolymerizable detector with ultraviolet coherent light.

United Str Y. 3040M 4 3031; [in 3,716,286 51.101111 et a1. X 39% Feb.13, 1973 1 1 HOLOGRAPHIC TELEVISION RECORD 1967 pp. 341-342.

SYSTEM Gerritsen et al., Applied Optics, Vol. 7, No. l 1, Nov.

9 [75] Inventors: Daniel S.- St. John, Hockessin; Ken- 68'pp neth A.Haines, Mlddletown, both of Primary Examiner Dav-ld schonberg AssistantExaminer-Ronald J. Stern [73] Assignee: Holotron Corporation,Wilmington, & washbum Del. [57] ABSTRACT [22] Filed: Dec. 11, 1969 Amethod and apparatus for constructing and replay- [2l] Appl. No.2 88 85ing an optical holographic record containing a plurality of very smallholograms, each of which contains in- 52 us. or. ..350/3.s, 178/5.4 E,355/2 "3 (her 5 l] m- Cl l G02, 27/00 preferred embodiment described,each frame of an or- (nary p g p movie is recorded as an in [58] Fieldof Search ..350l3.5, 355/2 dividua hologram The record is a narrow andelem gated film with the holograms formed in a line along [56]References Cited its length, each hologram touching those on either sideUNTED STATES PATENTS thereof. A moving image is reconstructed bydrayving the record'at a uniform speed through an effectively 3.610.72210/19 1 Be tenr inc et al continuous wave coherent light beam. A lightsensitive Kogelnlk detector for converting an image into a time varying3-530'442 9/1970 "350/35 electronic signal is positioned to receivereconstructed "f sequence of images and transform it into a signal ac-Cfl'l SCI! C 8 OTHER PU BLlCATlONS DeBitetto, Laser Focus, Vol. 4, No.17, Sept. 1968,

pp. 36-37. Stroke, Applied Physics Letters, Vol. 6, No. 10, May,

. Casler et 211., Applied Physics Letters, Vol. 10,.Iune

ceptable to an ordinary television set for displaying the movie thereon.Each hologram is constructed by passing a beam of a coherent lightthrough a movie frame onto a much smaller hologram aperture and byterfermg this beam at a finite angle with a reference m wavefront havinga radius of curvature substantially equal to the effective distancebetween the movie and the hologram. Methods of adding color visualinformation as well as sound information are also disclosed. Such aholographic record is copied onto a photopolymerizable detector withultraviolet coherent light.

4 Claims, 47 Drawing Figures Q l t/ s/ 4/ 295 1 \l' 1 LASER J 1 I l 285ii ial PATENTEU Fem 3191s SHEET 01 0F mum/ 3 6158 QZEBHm PATENTEU FEB I3 I973 SHEET [12 0F LASER ELECTRONIC cmcuns IMAGE DETECTOR ELECTRONICCIRCUITS OUTPUT SIGNAL PATENTEU 3.716.286

SHEET 03DF 10 I 3 ae I 325 97 96 ELECTRONIC CIRCUlTS IMAGE DETECTOR 79OUTPUT 337 75 33s CIRCUITS l l \lvll LASER PATENTEU a; 1 1 6.286

' SHEET 0k 0F 10 EB I43 I37 ELECTRONIC E '35 PROCESSOR E |4| OUTPUT :39SIGNAL 1 Fig. 7

Fig. 9A Fig. 98 Fig. 9C

PATENTEDFEBI 31915 3.7 1 6 .286

SHEET USUF 10 Y-SIGNAL k (fly g I SIGNAL I57 I55 -J (7) 4 4-3 5 8 oIMAGE 5 l6! DETECTOR [63 i Q SIGNAL 5m 35 Fig l2 Fig. [4a Fig/4b FigFig. [3 (BLUE) (RED) (GREEN) PATENTEDFEBI 3l973 SHEET 07 F 4.5mmBANDPASS AUDIO FILTER 375) 37 5 EY 389 39I I 0-4MHz Y 53:? BANDPASS v EFILTER 1 81.0 385 BA A 0.5-1.5MH2 3-4MHZ A f ig a BANDPASS BANDPASS IFILTER FILTER SL 4 I 4.5mm WAVEFORM 373 4.5MHz BANDPASS 8383? FILTER z T3-5MHZ o 333MHz BALANCED SIGNAL 5|GNAL GENERATOR MODUYTOR GENERATOR 3871.0MHz l B D FREQUENCY 'ffi TRIPLER AUDIO RADIO OUTPUT To q 2/ FREQUENCYA coLoR TV MODULATOR REcEIvER ANTENNA RECEPTACLE 4I3 W SIGNAL Y ENCODEREY l F 35 3 S 397 3-4MHz BAL'ANCED 05-15mm L BANDPASS BANDPASS FILTERFILTER 4.5mm 407 I wAvEFoRM I 399 4.5MHz 0.333MH1 395 BAND PASS BANDPASS FILTER FILTER 4l5 T 0333mm 3.5MH1 BALANCED CLOCK SIGNAL GENERATORMODULATOR T FREQUENCY TRIPLER 1.0MHz BANDPASS FILTER I IIOLOGRAIIIICTELEVISION RECORD SYSTEM BACKGROUND OF THE INVENTION This inventionrelates generally to holography and more particularly to high densitystorage of visual information on a photosensitive record member.

The invention of off-axis holography is described by Leith and Upatnieksin the Scientific American, June, 1965, pages 25-35, and in theircopending patent application Ser. No. 361,977, now U.S. Pat. No.3,506,327. Briefly described, the basic off-axis holographic techniqueincludes interfering two mutually coherent beams of light at aphotosensitive detector and at some finite angle with each other. One ofthe beams contains in its wavefront the information to be recorded. Forinstance, one of the beams may be modified by an object. The other beamserves as reference energy and thus, the phase and amplitude of theinformation carrying wavefront are recorded on the hologram detector.The information carrying wavefront is reconstructed from the finishedhologram upon its illumination with coherent light in a beam that isphysically related to the reference wavefront beam used to construct thehologram. A viewer in the path of this reconstructed informationcarrying wavefront is able to observe an image of the original object infull three-dimensions as if he were observing the object itself.

Besides its utility in reconstructing images of objects in full threedimensions, the off-axis holographic recording technique is also usefulto record two-dimensional information in a manner employing theresolution capabilities of a photosensitive detector to better advantagethan do ordinary photographic techniques.

It is an object of this invention to provide a holographic recording andplayback technique which makes maximum use of the resolution capabilityof a photosensitive detector while maintaining acceptable reconstructedimage quality.

It is an object of this invention to provide a simple and economicalhologram record player.

It is also an object of this invention to provide a holographicrecording and playback technique for greatly reducing the area of arecord necessary to store a given amount of two-dimensional information.

It is a further object of this invention to provide a holographicinformation storage record containing a large number of independentitems of two dimensional information.

It is an additional object of this invention to provide a technique ofholographically recording an ordinary photographic movie onto a hologramrecord and to provide a technique of reconstructing a moving pictureimage from a hologram record for display on a television screen.

SUMMARY OF THE INVENTION Briefly described, the present inventioninvolves recording a plurality of very small holograms on a holographicdetector with each on a distinct surface area thereof, the individualholograms arranged for sequential read out. Each hologram is constructedof a distinct piece of two dimensional object information and occupies asignificantly smaller area on the hologram detector than the twodimensional extent of the object information recorded thereon. Thehologram record may be high resolution silver emulsion photographic filmor may be a photopolymerizable material, among others. The detector ispreferably elongated with the plurality of individual holograms arrangedin a line along the detectors length, each hologram touching or slightlyoverlapping those holograms on either side thereof.

After developing the detector in a manner appropriate to the typeutilized, a number of low-cost copy holograms are made thereof bypassing this hologram record and a photosensitive copy detector,preferably a photopolymer, through a coherent reconstructing light beam.When reconstructing light first strikes the hologram record on the sameside thereof that was illuminated during its construction, a portion ofthis light is diffracted by the hologram record in a manner to interferewith an undiffracted portion at the photosensitive copy detector. Afterprocessing the copy detector in -a manner appropriate to itsphotosensitive composition, a copy hologram record results which isreconstructed by drawing the record along its length through a coherentlight beam incident upon a side of said copy record opposite to thatilluminated during its construction. A portion of the coherentreconstructing light is diffracted sequentially by each individualhologram as it is drawn through the beam, thereby reconstructingsequentially the two dimensional object information pieces originallyrecorded on the hologram master. These images may be observed by the eyeor converted into some other form by an appropriate image detector.

The information which may be recorded on each hologram variesconsiderably and may include, for instance, printed documents of alltypes or digital information. In a preferred embodiment of the presentinvention, a hologram record is constructed which is capable ofreconstructing a moving picture. In this embodiment, each of theindividual holograms recorded has as its object information anindividual frame of an ordinary photographic moving picture. A movingpicture originally recorded on the photographic movie is reconstructedfrom the master or copy hologram record by drawing it at a uniform speedthrough a coherent light beam which is effectively a continuous wave. Apreferred use of economically constructed copy holograms of photographicmovies is for replay on a record player designed for attachment to ahome television receiver. Such a record player includes an imageconverting device such as a vidicon tube upon which are shown the imagessuccessively reconstructed from the successive distinct holograms of acopy hologram record, thereby to generate a time varying electronicsignal appropriate for displaying the moving picture on the face of thetelevision receiver.

Each individual hologram of the master record is constructed in a mannerthat an image reconstructed therefrom, or from a copy thereof, remainsstationary relative to a reconstructing coherent light beam even as themaster or copy record is moved through the reconstructing light beam.This is accomplished by constructing each hologram with the use of areference beam having a radius of curvature substantially equal to theeffective distance between the two dimensional object information andthe hologram detector. In one embodiment, the reference beam isdiverging and the two dimensional object information is positioned afinite effective distance from the hologram detector. In anotherembodiment, a collimated reference beam is employed in the constructionof each individual hologram with the two dimensional object transparencybeing effectively (apparently) positioned an infinite distance from thehologram detector by the use of appropriate optics.

When copies are made of the original master hologram record, thereconstructing coherent light beam is diverging or collimated, dependingupon whether the master hologram was made with a diverging or collimatedreference beam, respectively. When a copy hologram record isreconstructed, the reconstructing coherent light beam is eitherconverging or collimated depending upon whether the original hologramrecord was made with a diverging or collimated reference beam,respectively.

Although this summary generally outlines primary features of theholographic system of the present invention, there are many othersignificant details and combinations which will become apparent uponreading the following detailed description of the invention in itspreferred embodiments. The invention is described in this application isa holographic television record system but it is to be understood thatthe invention is not so limited, as defined in the claims appendedhereto.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1, 1A, 18, IC and ID illustratean arrange: ment for constructing a hologram record according to thisinvention;

FIG. 2 shows one specific form of a hologram constructed according toFIGS. 1 and IA;

FIGS. 3 and 3A illustrate in side and top views, respectively, thereconstruction of the hologram record shown in FIG. 2;

FIGS. 4 and 4A show certain modifications of FIGS. 1 and 1A;

FIG. 4B shows certain modifications of FIGS. 3 and 3A;

FIG. 5 illustrates a technique for constructing the color coded mastertransparency of FIG. 5A.

FIG. 5A shows a color coded master transparency for use in theconfiguration of FIGS. 1 and 1A to construct a hologram containing colorinformation;

FIG. 6 is a specific form of a hologram record con structed according tothe configuration of FIGS. 1 and 1A with the color coded mastertransparency of FIG. 5A as an object of the hologram;

FIG. 7 illustrates the reconstruction of the hologram record of FIG. 6;

FIG. 8 shows another color coded master transparency which may be usedas the object of a hologram record constructed according to FIGS. 1 andIA;

FIGS. 9 and I0 illustrate the construction of the color coded mastertransparency shown in FIG. 8;

FIGS. 9A, 9B and 9C are spatial filters for use in the optical systemsof FIGS. 9 and 10;

FIGS. 11 and 11A show two spatial modulating gratings used in theconfiguration of FIG. 10;

FIG. 12 illustrates the reconstruction of a hologram record made withthe color coded master transparency of FIG. 8 as an object thereof;

FIG. 13 shows yet another color coded master transparency;

FIGS. 14A, 14B and 14C show individual spatial modulating gratings foreach of the primary colors which are used in constructing the colorcoded master transparency of FIG. 13;

FIGS. 15 and I6 show alternate hologram records constructed according toFIGS. 1 and IA from the color coded master transparency of FIG. 13;

FIG. 17 illustrates the reconstruction of either the hologram recordshown in FIG. 15 or the hologram record shown in FIG. 16;

FIG. 18 shows an alternate form of the color coded transparency of FIG.13;

FIG. 19 shows a modification of the record player of FIG. 17 forreconstructing images from a hologram record constructed of thetransparency of FIG. I8;

FIG. 20 is a diagram of a two channel hologram record constructiontechnique utilizing electronic data processing.

FIG. 21 shows the reconstruction of a hologram record constructed by thetechniques illustrated in FIG. 20.

FIG. 22 schematically illustrates in one view an apparatus forconstructing a holographic sound track on the hologram record;

FIG. 22A shows a cross-sectional view of the apparatus of FIG. 22 alongthe line 22A-22A;

FIG. 228 shows a portion of the apparatus of FIGS. 22 and 22A with anenlarged scale;

FIG. 23 shows a holographic record including both color videoinformation and a holographic sound track;

FIG. 24 shows a side view of a record player for reconstructing videoand sound information from a hologram record such as that shown in FIG.23',

FIG. 24A is a top view of the record player of FIG. 24;

FIGS. 25 and 25A illustrate additional techniques for reconstructinginformation from a hologram record;

FIGS. 26 and 26A schematically illustrate in side and top views,respectively, a technique of copying a master hologram record;

FIG. 268 shows a modification of FIGS. 26 and 26A; and

FIG. 27 illustrates an alternate technique of copying a hologram record.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A holographic record forreadout through a television receiver preferably has the characteristicthat the record may be moved at a uniform speed past a readout station.Also, illumination of the record is preferably continuous to becompatible with holographic sound recording, or pulsed at a high ratewhich makes it appear continuous to an image detector, without need forshuttering or pulsing in synchronism with the film movement. Thisgreatly simplifies the record player and thereby makes it possible toproduce such apparatus at a reasonable cost and with high reliabilityfor use in the home as an attachment to an existing television receiver.FIG. 1 illustrates a side view of essential elements for constructingsuch a holographic record from an ordinary black-and-white photographicmovie. FIG. IA is a top view of the optical system of FIG. 1. A coherentlight source 11 generates a narrow beam of light 13 which is partiallyreflected by a beam splitter 53 into a light beam 14 which is thenreflected by a mirror 57, expanded by a lens and passed through apinhole filter 16 to form a diverging beam 17. The diverging beam 17 ispassed through an optical system 19 to produce a converging beam 21. Thebeam 21 is passed through the black-and-white photographic movie 23which is to be holographically recorded, thereby producing anobject-modified beam 24. The movie 23 is stored in some convenientmanner by a roll 25 and moved upward through the coherent light beam 21in response to an urging of an appropriate take-up reel 27. The movie 23is passed between flat glass member 29 and 31 which guide the film 23along a predetermined path through the coherent light beam 21. Anoptically clear liquid is contained between the members 29 and 31 toreduce friction of the film moving therebetween and additionally toserve as an optical "gate" by having an index of refraction intermediateof the index of refraction of the glass in the members 29 and 31 and theindex of refraction of the movie 23. Such refractive index matchingreduces reflections of light at the movie contacting surfaces of theglass members 29 and 31. The optically clear liquid is chosen to be onethat does not fluoresce at the wavelength of light emitted by the laser11. All optical elements used in constructing the hologram record arecarefully designed to prevent reflections which cause interferencepatterns that are recorded downstream at the holographic detector. Oneway to substantially reduce such reflections is to coat the elementswith an anti-reflection layer. Therefore, glass member 29 isanti-reflection coated at its incident surface 30 to reduce reflections.Similarly, the glass member 31 is anti-reflection coated at its exitsurface 32 to reduce reflections.

The optical system 19 is designed to image the pinhole of the pinholefilter 16 into a point much smaller than the size of an individualhologram to be con- \structed. This requires that extremely uniformsurfaces be provided on the individual elements of the optical system19. The beam control system 19 is preferably positioned in the movietransparency illuminating beam before the transparency, as shown, but,alternatively, a portion of the optics may be placed in theobject-modified beam 24 downstream of the movie 23.

The optical system 19 is carefully controlled to eliminate bubbles,scratches, dirt, and other light scatterers from the light beam path,thereby maintaining a uniform intensity across those planes of thecoherent light beam 21 at which the movie 23 is likely to be placed.Eliminating the light scatterers in the light beam path prevents theformation of annoying diffraction patterns which result frominterference of light scattered by such imperfections with thesubstantially uniform wavefront which passes through a non-diffuseobject transparency such as the movie 23.

The individual hologram size and shape is determined by an aperture 45of a mask 33 placed in front of a photosensitive hologram detector 35.The detector 35 is in the form of an elongated thin flexible film storedon an appropriate reel 37 and drawn behind the mask 33 onto a take-upreel 39. Glass members 41 and 43 are provided on either side of thedetector 35 to provide support thereof and with a liquid optical gatetherebetween to reduce reflections. Also, the incident surface of theglass member 41 and the exit surface of the glass member 43 areanti-reflection coated or otherwise treated to prevent significant lightreflection at these surfaces. The aperture 45 of the mask 33 may haveany one of a wide variety of shapes and for the specific movieembodiment described herein, the aperture 45 is preferably square orrectangular.

Each frame of the movie 23 is recorded onto an individual hologram atthe holographic detector 35. An appropriate motor and gear drive 47 isoperably connected to the take-up reel 27 for advancing the movie 23between frames. Similarly, a motor and gear apparatus 49 is operablyconnected to the take-up reel 39 for simultaneously advancing theholographic detector 35. The coherent light source 11 is preferably apulsed laser with sufficient intensity to record a hologram of a singleframe of the movie 23 in one pulse. Between pulses, the movie 23 isadvanced to place a new frame within the light beam 21 and theholographic detector 35 is simultaneously advanced an amount to place anunexposed portion of the detector behind the aperture 45. Suitableautomatic equipment may be employed, including a common electroniccontrol 51, for synchronizing the laser pulses with the movie anddetector advance. The hologram detector may be advanced intermittentlybetween laser pulses or may be advanced uniformly if the laser pulse isshort enough. Similarly, the movie film may also be advanced eitherintermittently or uniformly.

The hologram detector 35 is placed in the objectmodified beam 24 infront of or behind the point focus of the beam 24 which represents animage of the pinhole filter 16. Furthermore, the detector 35 ispositioned at a plane of substantially uniform intensity thereacross inthe absence of the movie 23. This positioning avoids introducingdistortions into a reconstructed image which are caused by overdriving ahologram detector with light intensity in one small portion thereofwhile underdriving the detector in other areas thereof.

In order to record holographic information on the detector 35, areference beam is required for interference with the informationcarrying beam 24 at the detector 35. The reference beam is provided bypassing a portion of the intensity of the beam 13 through the beamsplitter 53 to provide a beam 55 which is then passed through a lens 59which brings the beam to a point focus in an aperture 61 of a pinholemask 63. Beyond the point focus 61, a diverging beam 65 illuminates theholographic detector at a finite angle 0 with the information carryingbeam 24 to form a hologram each time the coherent light source 11 ispulsed. In order to be able to reconstruct a holographic recordconstructed in this manner with a continuous motion of the hologramrecord and with a shutterless continuous wave laser, the point focus 61of the reference beam is located a distance from the hologram detector35 that is the same as a distance between the movie 23 and the hologramdetector 35. That is, the wavefront reference beam 65 striking theholographic detector 35 is given a radius of curvature substantiallyequal to the distance d shown in FIG. 18 between the movie and thedetector. This radius of curvature may be provided by a wide variety ofspecific optical arrangements other than that illustrated in FIG. 1, asis well known.

it will be noted from FIG. 1 that the reference beam point focus 61 liesin a plane that is perpendicular to the detector 35 and that intersectsit in a line across the detector normal to its length and passingthrough the aperture 45. That is, in FIG. I, the rays of the referencebeam 65 are substantially normal to the motion of the detector 35. Withthis angle of intersection of the reference beam with a detector offinite size, a hologram record so constructed has image motion uponreconstruction that is less than that image motion which results from ahologram constructed with some other reference beam angle ofintersection.

Since the reference beam 65 passes through the aperture 45 in therecording of each hologram, annoying diffraction patterns may beproduced by the aperture 45, particularly if the aperture has sharpedges. These diffraction patterns will be recorded by the hologram and,if they fall in the image field, they will produce undesirable noise.This effect can be overcome by spatially arranging the image field withrespect to diffraction patterns, and/or by specially designing theaperture 45. One technique is to construct each hologram to locate itsreconstructed image so that it is spatially separated from thediffraction pattern produced by the aperture 45, either by making thereference beam angle sufficiently large or by locating the image awayfrom the diffraction pattern of the aperture. For, instance, thediffraction pattern from a square aperture forms, upon reconstruction ofan image, two perpendicular lines passing through the aperture. Thus,with this pattern, the area lying along diagonals of the diffractionpattern is free of diffracted light and the image can be located inthese regions.

Another and perhaps preferred method to minimize the aperture causednoise is to apodize the aperture so that the aperture has a transmissionfunction that is a gradual change from the minimum to maximum values asopposed to the step transmission function associated with an aperturewith sharp edges. This apodized aperture will then produce a diffractionpattern in which most of the diffracted light is located in the nearvicinity of the reference beam and thus will not extend very far towardthe image field.

Referring to FIG. 18, certain elements of FIG. 1A are repeated withdistances and element sizes indicated. The extent 1: of the hologramaperture 45 is chosen to be small enough to minimize the size, and thusthe cost of the final hologram record which includes a large number ofsmall holograms, each having substantially the area of the aperture 45.Once a: is determined, the photosensitive detector 35 is positioned adistance d from the movie 23 that is small enough to give areconstructed image resolution that is as good as that required for aparticular application. Once x and d have been determined, the f-numberof the optical system 19 follows.

Considering a specific example wherein images from a hologram record areto be reconstructed through an ordinary television apparatus, eachreconstructed image should have a resolution of about 500 elements sincetelevision resolution capability is about 500 lines per frame. That is,the resolution element size 6 of a reconstructed image from the hologramrecord should be about m/SOO, where m is the extent of the movie 23being recorded, as shown in FIG. 18. For a hologram of the typeconsidered herein,

8=L54 A/sina (I) where A is the wavelength of the light utilized and ais the angular size of the hologram aperture 45 as viewed from the movie23. For a small angle a, as is the case here, sin a it x/d. Therefore,

d ax/LMA (2) In a typical application of the techniques herein, themovie 23 is of the 35mm. variety wherein each frame has a maximumdimension of about m 20mm. Therefore, 8 20mm/500 or 0.04mm. A convenienthologram size (and thus the size of the aperture 45) for economy in thesize of the completed hologram record is about x lmm. Substituting thesevalues into equation (2) gives a distance between the detector 35 andthe movie 23 of d i! 43mm. when light having a wavelength A 0.6 X 10 mm.is employed. By the geometry of FIGS. 1-1C, therefore, the f-number ofthe optical system 19 should be about d/m, or, in this specific example,approximately 12. The minimum resolution capability required of thehologram detector is determined by the f-number of the system and thelight wavelength.

It may be noted from this example that the light wavelength A is withinthe visible spectrum in the red region. It may be noted from equation(I) that if the wavelength is made shorter, the resolution element size8 decreases, thereby increasing the resolution of the system. Thewavelength utilized depends upon laser availability and characteristicsof the photosensitive material used in the hologram detector. Aphotopolymerizable material that is sensitive to ultraviolet radiationin the near visible region may be utilized, as described in detailhereinafter. Radiation having a wavelength A 0.35 X 10" mm. To which aphotopolymer material is sensitive may be generated by an availableultraviolet laser, thereby to increase the resolution capability of anoptical system designed for use with visible light radiation.

After recording the photographic movie 23 one frame at a time onto theholographic detector 35 and after processing the detector, a holographicrecord 35' results, a portion of which is illustrated in FIG. 2. Forthis record, a plurality of holograms are constructed with asubstantially square aperture 45 in the configuration of FIGS. 1 and IA,each hologram containing information of one frame of the movie 23. Eachhologram illustrated here is about 1 mm. square on a flexible filmrecord with a width of about 4 mm. Each individual hologram is placedonto the film 35 so that it just touches those on either side of it, orperhaps even with some overlap, to prevent flicker duringreconstruction. The individual holograms constructed may be circular butsuch a shape is not preferred since less efficient use of availabledetector area results as well as flicker due to some space betweenindividual holograms.

As can be seen from a portion of the holographic record 35' shown inFIG. 2, there has been a drastic reduction in the amount of filmnecessary to store the information formerly stored on ordinaryphotographic film. The usual 35 mm. movie has an individual frame sizeof I4 mm. X 20 mm. which may be recorded on an individual hologram 1 mm.square. The length of a holographic record constructed according to thetechniques of this invention is approximately 7 percent of the length ofa 35 mm. movie. Also, it can be seen from FIG. 2 that even with a narrow4 mm. hologram film record width there remains room for another channelof picture information or the addition of color information, as well asa channel of continuous sound information.

The holographic record 35 of FIG. 2 is reconstructed according to thetechniques illustrated in FIGS. 3 and 3A. FIG. 3 represents a side viewof a hologram record player and FIG. 3A is a top view. The holographicmovie 35' is stored on an appropriate reel 69 and transferred to atake-up reel 71 at a uniform speed by some appropriate motor source 73.A mask 75 having an aperture 77 corresponding to the dimension of theindividual holograms on the holographic record 35', and thuscorresponding to the dimensions of the hologram aperture 45, is placedalong one side of the continuously moving holographic record 35'. Theaperture 77 may be apodized to reduce diffraction noise in areconstructed image. This aperture is illuminated by a low powercontinuous wave laser 79 whose narrow beam 81 is passed through apinhole filter 83 to improve its spatial coherence, and then is formedby an optical element 85 into a converging beam 87. A portion of theintensity of the constructing light beam 87 is diffracted into an imagecarrying first order beam 89 by a hologram recorded on the holographicrecord 35'. An image 91 is fonned in the diffracted first order beam 89in real space. A zero order light beam 93 (undiffracted) comes to focusat a point 95 which is the center of curvature of the beam 87 and is outof the path of image carrying beam 89. The image 91 is located inrelation to the zero order point focus 95 as the movie 23 of FIGS. 1 and1A is located in relation to the reference beam focal point 61 duringthe hologram construction. The curvature of a reconstrucing light beamin holography is generally chosen to be substantially the same as thereference beam used in constructing the hologram in order to preventimage distortion. However, distortion between the radial and lateralmagnifications of a reconstructed image is unimportant for theapplication herein since only a two dimensional reconstruction isdesired. Therefore, the precise degree of curvature of thereconstructing light beam 87 is not so restricted herein for imagequality. The reconstructing light beam 87 strikes the hologram 35' fromthe side opposite that illuminated during its construction and with anopposite curvature direction, in order to directly reconstruct an imagein real space. The precise degree of curvature of the reconstructingbeam 87 and its angle of intersection with the hologram record 35' arechosen to reconstruct an image of a proper size for matching the size ofan image detecting tube 96. A simplified apparatus for controlling thisbeam curvature is described hereinafter with respect to FIGS. 4B and 23wherein a lens is placed on the image side of the hologram record.

The image detector 96 converts intensity variations across thereconstructed image 91 into a time varying electronic signal. An imagedetector suitable for use herein, such as a television camera tube, avidicon tube or a photodetection matrix, is commercially available. Atime varying electronic signal 97 representing a raster scan of thereconstructed image is connected with a television receiver (not shown)for displaying thereon a movie from the holographic record. As onehologram recorded on the holographic record 35' moves out of theaperture 77 and another hologram moves within the aperture, the image 91changes from that recorded on the one hologram to the image recorded onthe other hologram. The images do not move across the face of the imagedetector as the individual holograms are moved past the aperture 77.This results primarily from the curvature control of the reference beam65 as described hereinbefore. An image 91 reconstructed from the onehologram merely fades out as an image formed from reconstruction thenext adjacent hologram fades in while superimposed on the image formedfrom the prior hologram. It is this characteristic of a holographicrecord constructed and reconstructed according to the techniquesoutlined herein that plays a significant part in making it possible fora simplified record playback apparatus. The successive formation ofimages in this manner provides information for the image detector whichis the same as it would receive if scanning the real world through theoptical system of a television camera. It should be noted that thischaracteristic eliminates the need for recording a synchronizing pulseon the holographic record to control the image detectors raster scanningof the image. The holographic record making operation is additionallysimplified since ordinary photographic movies of varying frame rates mayall be constructed in the same manner; that is, one small hologram isconstructed for each frame of the film. The continuous speed at whichthe holographic record 35' is moved during reconstruction is ultimatelydetermined by, among other factors, the frame rate of the photographicmovie recorded thereon but there is no need to match this frame ratewith that of the image detectors.

The electronic signal 97 is processed by appropriate electronic circuits99 which may be designed to produce an output signal for connection withthe internal circuits of a television receiver but preferably includescircuits for modulating the picture signal 97 onto a radio frequencycarrier so that the output signal may be fed into the antenna jack of ahome television receiver. This preferred apparatus allows for connectinga holographic record player to an individual television receiver withoutneed for its modification.

A hologram record constructed and reconstructed according to thetechniques illustrated in FIGS. l-3A is subject to being scratched andhaving dirt particles adhere thereto. If this occurs in an area of arecord where a hologram is recorded, the image reconstructed from thathologram is likely to have diffraction pattern noise superimposedthereover. The movie illuminating beam 21 of FIGS. 1 and 1A is carefullycontrolled to have a highly uniform wavefront striking the movie 23.Upon reconstruction of a hologram, this highly uniform wavefront isreconstructed in the beam 89 of FIGS. 3 and 3A. Any dirt or scratches onthe hologram scatter a portion of the reconstructing light beam 89intensity. This scattered light interferes with the highly uniformreconstructed wavefront to form diffraction patterns at the plane of theimage 91. Therefore, a hologram record is coated with a material toreduce the likelihood that scratches or dust will become a part of therecord. Also, the mechanical components of the record player arecarefully designed to reduce scratches and dust.

However, in order to provide a long life hologram record capable of alarge number of plays, it is also desireable to construct each hologramin a manner to be less sensitive to dust and scratches. This may beaccomplished by modulating the object illuminating beam 21 of FIGS. 1and 1A in a particular manner so that the wavefront striking the movie23 is no longer highly uniform in phase and amplitude across the beam. Amodification of FIG. 1A is shown in FIG. 1C wherein a modulatingstructure 68 is inserted in the path of the beam 21. One method ofmodulation utilizes a structure 68 which imparts either a period phaseor a periodic amplitude variation across the beam as it passes throughthe movie transparency 23. When an image is reconstructed from ahologram so constructed, any scattered light due to scratches or dirt onthe hologram will interfere with a periodically phase or amplitudevarying wavefront in the plane of the image 91. The diffraction patternis thereby broken up and is not as objectionable to the viewer of thereconstructed image. Furthermore, if the period of the phase oramplitude variation is chosen to be less than an image elementresolvable by the viewing system including a television set and theimage detector 96, the pieces of the diffraction pattern remaining arenot observable by a viewer of the television set. These pieces merelyadd to the intensity of a resolvable element of the image 91 that islarger than the pieces of the diffraction pattern. One way ofaccomplishing such modulation of the beam 21 is described in AppliedOptics, vol. 7, No. 11 (November, 1968), pages 2301-231 1. This articledescribes the use of an intensity varying difiraction grating for themodulating structure 68 to illuminate a transparency with a wavefrontwith periodic variations thereacross.

In place of an intensity varying grating 68, a dispersion plate having auniform amplitude transmission thereover and a rapidly varying phasethereacross may be utilized. As pointed out by Upatnieks in Appliedpn'cs, Vol. 6, No. 11, November, 1967, pp. 1905-1910, and in thecopending patent application Ser. No. 638,031, now U.S. Pat. No. 3539241if such a dispersion plate is positioned POSITIONED immediately againsta transparency in its illuminating light beam the transparency isilluminated with uniform amplitude but rapidly varying phasethereacross. In the optical system of FIGS. 1 and 1A, the transparentmember 29 may be modified by toughening its surface immediately againstthe object transparency 23. The roughened surface provides illuminationof the transparency with varying phase thereacross.

Instead of the random phase variation suggested as a specific example byUpatnieks, it is preferable to impart a periodic phase variation to thetransparency illumination for the systems described herein. A randomphase variation may have the disadvantage that some of the pieces of anundesirable diffraction pattern may be so large as to be resolvable bythe viewing system. Referring to FIG. 1D, the optical plate 29 of FIGS.1 and 1A is shown in partial cross-section after conversion into adispersion plate 29' by adding to the surface thereof adjacent to thetransparency 23, periodically recurring undulations 34 of asubstantially uniform period of recurrence. The undulations arepreferably parabolic in shape to reduce undesired light scattering but asinusoidally varying surface is a close equivalent and perhaps moreeasily obtained. The optical member 29' is most conveniently constructedby plastic molding techniques.

No matter what specific type of modulating structure is utilized, thehologram aperture 45 must generally be larger than the minimum sizecalculated according to the considerations hereinbefore discussed.Diffraction by a modulating structure enlarges the object-modified beam24 and thereby requires a larger hologram aperture if information of themovie frame is not to be lost and to prevent a speckled reconstructedimage. Such diffraction constructs multiple holograms of the sameinformation. Other techniques for multiple hologram construction thanthe diffusion (diffraction) techniques described herein may also beemployed to provide the redundancy required. Such a technique, forinstance, is to construct a plurality of adjacent or slightlyoverlapping holograms of the same information by multiple exposure.

The hologram record construction techniques described with respect toFIGS. 1 and 1A have utilized a diverging reference beam. It is generallymore convenient to use a collimated reference beam in order to simplifythe copying of such a hologram record and its reconstruction, as willbecome apparent hereinafter. The diverging reference beam exampledescribed hereinbefore provides a wavefront at the hologram detectorhaving a radius of curvature equal to the effective distance between theobject transparency and the hologram detector in order to produce asequence of holograms which can be reconstructed without individualimage motion. A collimated reference beam has a wavefront striking ahologram detector with an infinite radius of curvature. Therefore, theobject transparency to be recorded must be effectively placed aninfinite distance from the hologram detector in order to avoid imagemotion upon reconstruction of the sequence of holograms on a hologramrecord. Such a technique is described with respect to FIGS. 4 and 4Awherein the elements thereof which are the same as those describedpreviously in FIGS. 1 and 1A are given common reference characters.

The collimated reference beam 55 of FIGS. 4 and 4A originates from thecoherent light source and is directed through the hologram aperture 45onto an elongated hologram detector 325 without curvature controllingoptics placed in its path, although optical elements may be used forvarious reasons. The object movie transparency 23 is generallyilluminated as in FIGS. 1 and 1A except that the diverging coherent beam17 of FIGS. 4 and 4A may conveniently be passed through an opticalelement 327 to form a collimated light beam 329 for illuminating themovie 23, thereby producing an object-modified beam 331. In order toplace the object movie transparency 23 at effectively an infinitedistance from the detector 325, a lens element 333 with a focal length fis positioned in the object-modified beam 331. The lens 333 ispositioned so that the object movie transparency 23 is located at onefocal plane thereof and the hologram detector 325 is positioned in thevicinity of the other focal plane of the lens 333 such that the hologramaperture 45 of FIGS. 4 and 4A is uniformly illuminated in the absence ofthe transparency 23. Additionally, the aperture 45 is positionedrelative to the lens 333 to capture the full converging portion of theobject-modified beam 331 when the transparency 23 is removed. Such aconfiguration utilizes the lens 333 in performing a Fourier transform ofthe information contained on the object transparency 23, therebyeffectively positioning the object transparency 23 an infinite distancefrom the hologram detector 325. The curvature of the reference beam 55also has an infinite radius, thereby to produce a hologram record fromwhich images may be reconstructed from sequential holograms withoutimage movement. Mathematical details of such a hologram are given in thebook Introduction to Fourier Optics by J.W. Goodman (McGraw-Hill, I968),beginning at page Hi. Additionally, to further minimize any possibleimage movement upon reconstruction, a reference beam 55 is orientedperpendicular to the hologram detector 325 in a direction of intendedmovement of the detector 325 upon reconstruction.

This description uses the term effective distance" when referring tocertain distances between elements of an optical configuration. As usedherein, the "effective distance" between elements of an opticalconfiguration is that actual distance that appears to exist between theelements because of some light controlling optics intermediate of thetwo elements whose actual physical separation is some other value.

After processing the exposed photosensitive detector 325 in anappropriate manner, an elongated hologram record 325' is preferablyreconstructed as illustrated in FIG. 48. Those elements common with therecord player described hereinabove with respect to FIGS. 3 and 3A aregiven common reference numerals. A collimated beam 335 from the laser 79is directed against the hologram record 325' without optical elementstherein (although optics may be used) so that the record is illuminatedwith collimated reconstructing light. A lens 337 is positioned in afirst order beam diffracted by the hologram record to reconstruct animage in real space at some finite distance from the hologram record.The lens 337 is chosen to give a magnification of the reconstructedimage 91 appropriate for the particular image detector 96.

The hologram record 325 may be reconstructed with a converging lightbeam 87 as illustrated with respect to FIGS. 3 and 3A but it ispreferred to illuminate the record itself with a collimated beam 335 asshown in FIG. 4B. This is preferred since the reference beam used inconstructing the hologram record is itself collimated. Therefore, if aphotosensitive detector 325 has some finite thickness (as is preferredfor bright reconstructions) the Bragg condition may be more nearlysatisfied upon reconstruction by a collimated beam.

The techniques described hereinabove have assumed a black-and-whitephotographic movie 23 as the subject for constructing the holographicrecord. If it is desired to use a color movie as the subject, ablack-andwhite copy thereof is made with white light according to thephotographic techniques of contact printing. This black-and-white copyis then used as the object for construction of a holographic recordaccording to FIGS. 1 and 1A. The reason that the color movie should notordinarily be used directly is that the coherent light source 11 emitslight of only one color which significantly distorts the color balanceof a color movie used to make a holographic record directly.

In addition to using an ordinary photographic movie as the subject for aholographic record, video information stored on magnetic tape or someother medium may also be transferred to a holographic record constructedaccording to the techniques outlined herein by first making ablack-and-white photographic movie frame by frame from the tape or someother medium through a television monitor or other signal recordingmeans known in the art. This movie may then be used as subject of theholographic record constructed according to either the techniquesillustrated in FIGS. 1 and 1A or those illustrated in FIGS. 4 and 4A.

An output signal of the apparatus illustrated in FIGS. 3 and 4B iscarried by a radio frequency carrier for connection with the antennajack of either a black-andwhite or color television receiver. Thematerial viewed on the television receiver will be that informationrecorded on the black-and-white ordinary photographic movie utilized assubject of the holographic record. A holographic record capable ofreconstructing color information to display a color photographic movieor a television magnetic tape signal on a color television set ispossible by an extension of the techniques described with respect toFIGS. 1-4B. Improvements thereon which make possible color informationreconstructions from a hologram record as described hereinafter areclaimed in an application by Daniel S. St. John entitled HolographicColor Television Record System filed concurrently herewith.

In all three alternate color methods described herein, the colorinformation is not directly recorded onto a hologram record, as it couldbe according to the known techniques of color holography, but instead isprocessed prior to making the holographic record according to thetechniques of this invention. This prior processing provides a hologramrecord which may be replayed on a home color television receiver with aminimum of additional apparatus. Neither complicated color separatingand modulating optics nor more than one monochromatic reconstructinglight source is required in the record player. The first of thesealternate color techniques is illustrated with respect to FIGS. 5-7wherein an ordinary photographic color movie is the subject of ahologram record.

FIG. 5A shows ablack-and-white color coded master film transparency 103containing color information of a color movie. Each frame of the colormovie is recorded on the black-and-white film 103 a total of threetimes; a transparency 15 recording the red information of the colormovie frame, a transparency 107 recording the green information, and atransparency 109 recording the blue information. The resultingblack-and-white film 103 is then used as the object transparency of thehologram record constructed according to the configuration of FIG. 1 andis substituted for the movie 23 therein.

A technique of constructing the black-and-white film 103 is illustratedin FIG. 5 where a while light source 111 emits radiation which iscollimated by a lens 113 and passed through a color filter position 115before striking the color movie 117. If a color filter placed at theposition 115 allows only the red component of the white light sourceemission to pass through the film 117, the light beam I19 contains redinformation of the color film 117. The beam 119 is focused by lenses 121and 123 onto a portion of the film I03 and recorded thereon. Anadjustable aperture 125 is provided a distance equal to the focal lengthaway from each of the lenses 121 and 123 (the frequency plane) and maybe adjusted to limit the spatial frequencies recorded on the color codedfilm 103. Limitation of the spatial frequencies recorded on the colorcoded film 103 may be desired to that light is not diffracted outsidethe hologram aperture when the hologram record is constructed. However,if limitation of the spatial frequencies recorded on the color codedfilm 103 is not desired, the film 103 could be constructed according toordinary contact printing techniques of photography.

A mask 127 is placed over the film 103 and contains an aperturepositioned to limit recording red information along the left handportion of the film 103. The color film 117 and the black-and-white film103 are moved at a proper relative speed, or may be advanced togetherone frame at a time to initially record all the red information of acolor movie 117. The next step is to repeat this recordation bysubstituting a green for a red filter at the filter position 115 andrealigning the optical elements including the mask 127 so that the greeninformation is recorded in the middle of the film 103. Similarly, blueinformation is then recorded on the right hand side of the film and withthe use of a blue filter placed at the position 1 15.

When developed, the film 103 is substituted for the photographic movie23 in the configuration of either FIGS. 1 and IA or FIGS. 4 and 4A tomake a hologram record. The aperture 45 therein may be rectangularinstead of a square used hereinbefore as a convenience in constructionsince the information recorded on each hologram is rectangular with onedimension thereof considerably greater than the other dimension. Aportion of the hologram record is shown in FIG. 6 with a row ofrectangular holograms 129 just touching or slightly overlapping eachother. An individual hologram 131, for instance, contains full colorinformation of one frame of the color movie 117. The hologram I31 hasbeen made of its red, green and blue components recorded in theintermediate step on the black-andwhite film 103. Alternatively,individual hologram may be constructed for each of the three primarycolor components but this is not preferred since the detector area isnot efficiently utilized. Yet another alternative, which is preferredfor efficient utilization of the detector area, is to construct a singlesubstantially square hologram corresponding to each color movie frame,thereby constructing a hologram record with an appearance similar tothat of FIG. 2. In order to construct square holograms according toFIGS. I and 1A from the horizontally elongated information bits of FIG.5A, the optical system 19 of FIGS. 1 and IA is provided with acylindrical lens element (not shown) which converges the object-modifiedbeam 24 more in the horizontal direction than in the vertical direction.

The hologram record 35" (or a record constructed according to thealternatives described hereinabove) is reconstructed by being driven ata uniform speed, as described herein with respect to either FIGS. 3 and3A or FIG. 4B. The laser, associated optics, and preferred curvature ofthe reconstructed beam are the same in reconstructing the hologramrecord 35" as were described with respect to FIGS. 3 and 3A inreconstructing the hologram record 35' and as described with respect toFIGS. 48 in reconstructing the hologram record 325'. The hologram record35 is shown in FIG. 7 being drawn out of the paper continuously and at auniform speed through a monochromatic coherent light beam 87. Eachhologram thereon reconstructs three monochromatic images, an image 133containing red information of a color movie frame, an image 135containing green information of the movie frame, and an image 137containing blue information of the movie frame. Each image, of course,is the color of the laser light beam 87. An individual image detentiontube is aligned with each of the three reconstructed images, an imagedetector 139 generating a time varying electrical signal E correspondingto the red information of the color movie, an image detector 141generating a signal E corresponding to the green information of thecolor movie and an image detector 143 generating a signal E proportionalto the blue information of the color movie. These color signals aregamma corrected, appropriately added and subtracted to produce standardluminance and chrominance signals required by a color television set,and modulated onto a radio frequency carrier by an electronic processor144 to produce an output signal which can be fed into the antennareceptacle of a home color television set. The home hologram recordplaying apparatus illustrated in FIG. 7 is only slightly more complexthan that illustrated in FIGS. 33A and 4B for black-and-white images.Three images detectors are included. A single monochromatic coherentlaser beam 87 is utilized for reconstructing the full color informationin three distinct images as recorded on the hologram record 35-. Therecord playing apparatus is similar to a three tube color televisioncamera without a complicated and expensive optical system for separatinga color image into its three color components. The system describedherein presents to the image detecting tubes directly from the hologramrecord the information each tube seeks, thereby simplifying the hologramrecord player.

Processing image information of each color movie frame to produce astandard FCC color electronic signal from the three primary colorsignals as indicated in FIG. 7 to yield a signal for utilization by acolor television receiver is accomplished in the electronic circuits ofthe record player. However, it is desired to minimize the complexity ofthe record player both in the required number of receiving tubes, suchas vidicons, and in the amount of electronic processing required. Forthis reason, the image information may be processed optically orelectronically prior to constructing the hologram record so that thereconstructed optical image signal presented to the record playerrequires only one or two detecting tubes, and after conversion into anelectrical signal, requires little or no electronic processing beforebeing received by a conventional color television apparatus.

The following specific example described with respect to FIGS. 8-12accomplishes such signal processing optically to give a signal that canbe recorded holographically and played out through a single imagedetecting tube. This example illustrates a second technique forconstructing a hologram record capable of reconstructing full colorinformation.

Referring to FlG. 8, a color coded master black-andwhite film 145 isconstructed as the result of a series of optical processing steps. Eachframe (such as frame 147) contains the processed information (signal) ofa distinct single color movie frame. Each frame (such as frame 147) thenbecomes the object of an individual hologram of a hologram record. Theframe 147 is constructed by being exposed a plurality of times to theinformation of a single color movie frame. During each exposure, theinformation is processed in a unique manner. The color picture signal M,as established by FCC standards, can be written,

M Ey+ E, cos (mt 33) E sin (mt-l- 33) where t= time color subcarrierfrequency (about 3.6 MHz) E luminance signal amplitude carried on a 4MHz bandwidth E, l-signal amplitude carried at 1.5 MHz bandwidth EQ-signal amplitude carried at 0.5 MHz bandwidth According to the FCC CCstandards, the following definitions apply:

Ey=0.30 E,+O.59 E, +0.11 E,

E, 0.60 E 0.28 E,,, 0.32 E,,,,

E red component of the total signal,

' E, green component of the total signal,

E, blue component of the total signal, and the subscript n refers to anarrow band-pass signal.

Since the phase of the color subcarrier must be accurately known toseparate the l and Q signals, and since this requirement may beincompatible with the linearity of the horizontal sweep of the detectingtube in the record player, it may be preferred that the hologram recorda modified signal M that is still easily interpreted by the home recordplayer in the form,

M=E +E,cosm,x+E cos m x (7 where x time or horizontal distant (relatedby the horizontal sweep frequency) w, carrier frequency of the l-signal(liq carrier frequency of the Q-signal For optical data processing, eachterm of Equation (7) is expanded by substitutions therein of Equations(4), (5), and (6), in which case the signal M is made up of E,, E,, andE signals that may be obtained by color filters. The optical processormust perform the functions of adding each of the color signals in theappropriate amounts, of providing the appropriate bandpass for the l andQ signals, and must modulate the l and O signals on their respectivecarriers. These carrier frequencies to, and m, are chosen to be abovethe 0-4 MHz range and are separated sufficiently to avoid cross-talk.Addition of signals is accomplished by successive exposures to eachcolor signal where the constants that are part of each such signal termare obtained by a light attenuator or by appropriate control of theexposure time. The lowpass signals are obtained with the use ofappropriate spatial filters in the spatial frequency plane of theoptical processor. The carrier frequency terms are obtained by thesuperposition of a grating having the proper spatial frequencyfNegativecarrier frequency terms are recorded by displacing the grating 180. Acomplication occurs, however, because recording a signal through agrating records not simply the signal multiplied by cos wx but ratherthe signal multiplied by [9% h cos my]. That is, there is an averageexposure through the grating that appears as a signal term at lowspatial frequencies, in addition to the desired signal at the carrierfrequency modulated with appropriate side bands. For this reason, therecording of the unmodulated Ey signal is modified so that the sum ofthat recording and the unmodulated components of the l and Q signals(recorded through the gratings) add up to the desired unmodulatedsignal. In addition, it is necessary to increase the relative strengthof the Ey signal, since there can be no negative terms in the recordingsteps. Thus, the signal actually recorded on the film 145 may be amodified signal M" instead of the signal M defined in Equation (3):

M"=3E +lE,cosw,x+%E cosw x 8 Compensation for the changed relativesignal strengths of Equation (8) is accomplished by simple electroniccircuits in the record player. FIGS. 9llA show a specific method ofrecording on a frame 147 of the black-and-white film 145 the signal of asingle frame of color movie 117 according to Equation (8).

FIG. 9 shows one optical configuration for recording the unmodulatedterms of Equation (8) and FIG. 10 shows a corresponding opticalconfiguration for recording the carrier frequency terms. Elementstherein corresponding with those of FIG. 5 are given the same referencenumbers. The light source 111 is a balanced polychromatic one. ltsoutput is filtered into a red, green or blue component by an opticalfilter placed at the plane 115. A spatial filter placed at the positionlimits the bandwidth of the signal recorded on the film 145. The shapesof such filters are shown in FIGS. 9A, 9B, and 9C. An A filter in FIG.9A has a hole 126 in an otherwise opaque substance to limit theunmodulated signal terms recorded to 0-4 MHz. The size hole toaccomplish this depends upon the horizontal line scan frequency of thedetector tube, and upon the wavelength or color of light used in thesignal processor. An A, filter of HG. 98 has a smaller hole 128 forrecording the narrower bandwidth l signal terms. An Aq (not shown)filter is similar to the A, filter of FIG. 9B but has an even smalleropening reflecting the smaller bandwidth of the Q-signal terms. An A,filter, Q-signal in FIG. 9C, has an annular hole 130 to provide aband-pass between that of the l-signal and 4 MHz. The annulus has anouter diameter equal to that of the A filter, and a dark spot 132 in thecenter with a diameter equal to that of the hole 128 in the A, filter.Similarly, an A filter (not shown) has an annular hole to provide aband-pass between that of the Q-signal and 4 MHz. ln practice, thefilters should be apodized, that is, should have slightly blurred edgesso that distracting diffraction patterns from sharp edges thereof can beavoided. Thus, the A, A,, and A filters can be made photographically asnegative transparencies of slightly

1. A method of constructing copies of a light transmittive elongatedrecord with information holographically recorded by means of a referencebeam striking said record with rays perpendicular thereto along itslength, comprising the steps of, drawing at a uniform velocity saidrecord and a photopolymerizable copy detector in the closest possiblecontact through a coherent reconstructing radiation beam first incidentupon said record and with rays thereof normal to the record along itslength, said beam illuminating a length of said record significantlyless than the total record length to be copied and said coherentradiation being of a wavelength to which said photopolymerizable copydetector is sensitive, and drawing the photopolymerizable copy detectoralong its length through an unmodulated radiation field that includesthe wavelength of said coherent radiation in a manner for any givenportion of the copy detector to be subjected to the unmodulatedradiation a few seconds after leaving the area of said coherentreconstructing radiation beam, whereby a copy hologram record isproduced.
 1. A method of constructing copies of a light transmittiveelongated record with information holographically recorded by means of areference beam striking said record with rays perpendicular theretoalong its length, comprising the steps of, drawing at a uniform velocitysaid record and a photopolymerizable copy detector in the closestpossible contact through a coherent reconstructing radiation beam firstincident upon said record and with rays thereof normal to the recordalong its length, said beam illuminating a length of said recordsignificantly less than the total record length to be copied and saidcoherent radiation being of a wavelength to which saidphotopolymerizable copy detector is sensitive, and drawing thephotopolymerizable copy detector along its length through an unmodulatedradiation field that includes the wavelength of said coherent radiationin a manner for any given portion of the copy detector to be subjectedto the unmodulated radiation a few seconds after leaving the area ofsaid coherent reconstructing radiation beam, whereby a copy hologramrecord is produced.
 2. The method as defined in claim 1 wherein the raysof said coherent reconstructing radiation beam further intersect saidrecord in a direction across its width to result in the maximum possibleintensity in a diffracted energy beam.
 3. Apparatus for making copies ofan elongated hologram record containing a plurality of individualholograms along the length of said record in touching relationship withone another, each hologram containing a distinct piece of informationand constructed with a collimated reference beam, comprising: means fordrawing said hologram record at a uniform speed through a copyingstation, means for drawing an elongated photopolymer copy hologramdetector past said reading station at the same uniform speed as saidhologram record, means for applying a vacuum between said hologramrecord and said copy detector for holding said detector in intimatecontact with said hologram record as they Pass through said copyingstation, means for generating and directing a coherent radiation beamagainst said hologram record in a manner that all rays thereof strikesaid record perpendicularly thereto in a direction along its continuousmotion, thereby to diffract light onto said copy detector, and anunmodulated light means positioned in the path of said elongatedphotopolymer copy detector for exposing said detector at least a fewseconds after it is exposed to said diffracted light.